amps = heat, the more amps you run through a motor the hotter it gets. That is what will kill a motor. Cooling the motor by way of it's location can allow you to run higher amps.
An enclosed motor will not last as long as oppossed to one mounted out in the air flow, From my own experience, Mega motors, they are rated at aprox 28 amps, yet due to location of them in my planes, I've run 50 amps through them with no harm.
Just like the engine in your car, with out cooling it isn't going to last long.
